Cathode ray tube with metallic tensioning ribbon for implosion protection



May 5, 1970 9 8 EN 6 0 5, Q .2 3 .M... G 4 N m .m, 5/ 1 N F 2 I Ff wMlDT

METALLIC TENS PROTECTIO 1968 P. SCH

RAY TUBE WITH BON FOR IMPLOSION Filed March 18,

CATHODE RIB United States Patent 3,510,589 CATHODE RAY TUBE WITHMETALLIC TENSION- ING RIBBON FOR IMPLOSION PROTECTION Peter Schmidt,Denkendorf, Germany, assignor to International Standard ElectricCorporation, New York,

N.Y., a corporation of Delaware Filed Mar. 18, 1968, Ser. No. 713,835Int. Cl. H01j 29/06 US. Cl. 1787.82 3 Claims ABSTRACT OF THE DISCLOSUREA metal tensioning strip is wrapped around a cathode ray tube at thefaceplate seam to prevent implosion. One end of the strip is secured toa mounting angle which is permanently positioned between the tube andthe overlapping layers of the strip as it is wrapped around. Theoverlapping portions are welded together to maintain the tension.

BACKGROUND OF THE INVENTION Field of the invention The invention relatesto a method to apply a tensioning strip which surrounds a cathode raytube in the zone of the seam between the cone-shaped body and thefaceplate portion, under a mechanical bias.

Description of the prior art The prior art already describes cathode raytubes around which are wound in the zone between the faceplate and theconical portion of the tube ribbons of plastic or artificial resin orother similar material such as hemp, cord, or other textile fabric orbraided ribbon of fibre glass, nylon, perlon or jute which are appliedwith the aid of a binding agent. In these arrangements the protectionagainst implosion is substantially achieved by the binding agent whichpartly penetrates into the ribbon and forms, after hardening, a uniformenvelope.

It is also known to use a shielding cap of ferromagnetic materialsurrounding the conical portion of a cathode ray tube said capconsisting of a metal ribbon wound in a suitable shape. Such a magneticshielding cap however is unsuitable to avoid implosions of cathode raytubes. From US. Pat. Nos. 2,785,820; 2,874,017; 3,220,- 592 and3,220,593 cathode ray tubes are known which are surrounded againstimplosion with a ribbon or strip being mechanically biased andconsisting of highly elastic material, applied onto the cathode raytubes at the critical zone. The mechanical biasing of the ribbon is madein most of the arrangements in that said ribbon or parts thereof are ledaround the cathode ray tube and mechanically tensioned or biased, whenconnecting the free ends of the ribbon or of the parts thereof with theaid of screws or of a turnbuckle.

Such a tensioning method shows the big disadvantage that the individualparts of the ribbon or strip or of parts thereof are extendeddifferently during tensioning which is extremely unfavorable for safetyof the tubes against implosion. The only method known, in order to applya tensioning ribbon which was uniformly expanded prior to itsapplication to the tube or the entire circumference, consists, accordingto said patent specifications in that the ribbon is uniformly heatedprior to its application onto the tube and is shrunk onto said tubeduring cooling. But this method has so many disadvantages that it wasnever applied in practice. The heated tensioning ribbon may easily causedamages of the tube; moreover, it is required, due to variations in thediameter of the tube, to use for each circumference a tensioning ribbonof a defined size, because such variations in circumference 3,510,589Patented May 5, 1970 cannot be compensated by the heating temperatureapplied to the tensioning ribbon, as the heating of the tensioningribbon is possible only Within a defined temperature range in order toavoid cracks in the glass due to a sudden heating. Finally thetemperature increase causes changes of the surface structure and of theappearance of the tensioning ribbon.

Another method in which a metallic tensioning ribbon is applied onto thecritical zone of a cathode ray tube under a uniform pulling stress, isdescribed in the French patent specification 1,406,501. In this methodone end of the ribbon is secured with the aid of a holding device,whereupon the ribbon is wound round the tube under a defined pullingforce and thereupon welded together. After welding, the weldingelectrodes and fixing claws of the holding device, arranged between thewall of the tube and the ribbon are removed. Thereby the tension of theribbon is reduced. To obtain a predetermined final tension of the ribbonit is therefore required to consider when tensioning the ribbon, theloss caused by removing of the fixing claws and of the weldingelectrodes between tube and ribbon. It is therefore necessary to tensionthe ribbon more when applying it than it is stressed or tensioned in itsfinal condition.

SUMMARY OF THE INVENTION It is the object of the present invention toprovide a method in which the tensioning ribbon possesses in its finalposition substantially the tension with which it was applied onto thetube. Another object of the invention is to fix, together with theapplying of the tensioning ribbon, the angles with the aid of which thecathode ray tube is mounted inside the equipment.

In a method to wind a metallic tensioning ribbon onto the critical zoneof a cathode ray tube under the application of a uniform pulling forceand the following welding of the tensioning ribbon one end of thetensioning ribbon is fixed, according to the present invention, at thelimb of the mounting angles of the tube within the housing, beingparallel to the sidewall of the tube and thereupon the tensioning ribbonis wound over the parallel limbs of the mounting angles and kept inplace by means of a holding device, and thereupon the overlapping partsof the tensioning ribbon are welded together.

Although a tensioning ribbon consisting only of one winding, results ina safe protection against implosion it may be of advantage forproduction reasons, that the tensioning strip or ribbon consists ofseveral windings one above the other. Such a tensioning ribbon mayconsist of an essentially thinner material for the individual windings.This has the advantage that the windings of thinner material fit thesurface of the critical zone still better than a single winding ofthicker material. It is of particular advantage to use the limb of oneof the fixing angles of the tube, being approximately perpendicular tothe wall of said tube as the current lead for the welding process.

The inventive method shows the advantage that between the wall of thetube and the ribbon to be wound around said tube neither temporaryremovable fixing devices nor welding electrodes must be provided. It isthereby achieved that the tensioning ribbon must be mechanically biasedduring its winding around the tube only to such an extent as it shouldbe in the final condition. Moreover the limb of the fixing angle beingapproximately perpendicular to the wall of the tube offers aparticularly favorable connection for one of the electrodes for thewelding of the tensioning ribbon. The other welding electrode is thenplaced on the appertaining portion of the tensioning ribbon, located onthe limb in parallel to the tubes wall.

3 BRIEF DESCRIPTION OF THE DRAWINGS The invention is now explained indetail with the aid of an example shown on the accompanying drawings.

FIG. 1 is a cross section of the cathode ray tube showing theoverlapping tensioning ribbon and mounting or fixing angles, and

FIG. 2 shows the method of Wrapping the ribbon around the tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT The cathode ray tube 1 ismounted in the device 2 and 2a. This mounting device may rotate aroundthe longitudinal axis in the direction of the arrow. Part 2 of thedevice is provided with a vacuum pump, the vacuum connection or outletdesignated by 8. The device 2a also accommodates fixing angles 3 whichkeep the tube in place after installation in the equipment. In theexample shown the metallic ribbon 4 is secured on the angle 3 at theleft side by welding or riveting. The ribbon 4 is reeled off from theribbon reel 5. In order to guarantee a uniform pulling force the reel isbraked by the brake 6 and the weight 7. By changing said Weight 7 thepulling force exerted on the ribbon during the winding can be changed.Instead of braking the reel it is also possible to have a weightdirectly effect the ribbon via a roller. The ribbon is Wound around thetube in such a way that the fixing device 2, 2a rotates together Withthe cathode ray tube 1 around the axis in direction of the arrow so thatribbon 4 is reeled off the reel 5 and wound around the circumference ofthe tube and around the limbs of the fixing angles, parallel to the tubewall. This winding process can be made in such a way that the tube issurrounded by one winding only; but also several layers of windings maybe provided..In such a case it is possible to use a substantiallythinner metal band and consequently also less pulling force. After thedesired number of windings has been applied onto the critical zone ofthe picture tube the ribbon is welded together in such a way that one ofthe welding electrodes is connected to the radially outward directedlimb of the fixing angle to which the ribbon has been welded, while theother Welding electrode is placed on the ribbon. After welding, theribbon is cut. By this cutting the pulling force exerted on the ribbon 4and maintained during the welding process, is cancelled. Instead ofhaving the tube rotating when applying the ribbon 4 it is also possibleto keep the tube steadily in place and to lead the ribbon reel 5 aroundthe tube, applying the desired uniform pulling force, until the desirednumber of winding layers are on said tube.

While only a single embodiment has been illustrated, other variationsmay be made in the method and configuration without departing from thescope of the invention as set forth in the appended claims.

What is claimed is:

1. A cathode ray tube protection device comprising a tube having aconical portion and a faceplate with a seam therebetween, mounting meansdisposed on the surface of said tube at said seam, a metallic tensioningribbon.

wrapped around the periphery of said tube over said seam, one end of theribbon being secured to said mounting means, a portion of said ribbonoverlapping said one end and an underlying layer and being welded tosaid No references cited.

RICHARD MURRAY, Primary Examiner R. K. ECKERT, 111., Assistant Examiner

